The Washington PostDemocracy Dies in Darkness

The incredible scale of the Strategic Petroleum Reserve, visualized

A maze of crude oil pipes and valves is pictured during a tour by the Energy Department at the Strategic Petroleum Reserve in Freeport, Tex., in 2016. (Richard Carson/Reuters)
5 min

A gallon of milk is about six inches square at the bottom. If you were to put four gallons together in a little square, then, you’d have a square foot of milk. That doesn’t capture the third dimension, of course; those jugs of milk with which we’re all familiar are a bit under 10 inches high. So you’d have a square foot of milk rising a bit under a foot off the floor.

Of course, you don’t have to fill those jugs with milk. You could fill them with, say, oil. Four gallons of oil sitting there on your living room carpet, contained by thin plastic. Not the best decision, but useful as an illustration.

I was curious, given the Biden administration’s plan to release oil from the nation’s Strategic Petroleum Reserve, exactly how much oil the United States keeps on hand. So I figured I’d convert it into something I can appreciate, like those milk jugs.

This did not work as intended.

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As would be expected, the United States has a lot of oil in the Strategic Petroleum Reserve. As of March 25, 568.3 million barrels, to be specific. And since each barrel contains the equivalent of 42 gallons of oil, that means that the United States has at its disposal 23.9 billion gallons of oil.

An amount that would take an awful long time to pour into 23.9 billion gallon milk jugs.

But now we do our math. If we were to fill those milk jugs and line them up for the nation’s eventual strategic use, we’d create a line of jugs about 63,000 miles long. Enough to run the distance of the Great Wall of China, and back, and then to the end again, and back and then almost back to the far end once again. If we arranged them in a square, it would cover about 35 square miles, a bit more than half of the entire area of D.C.

This is not a smart way to store this oil, of course, since it wastes so much space. Instead, we would be wise to stack the milk jugs vertically as well, so that we don’t use so much space. If we shaped our milk jugs holding our oil — about 3,400 jugs wide and long and a bit over 2,000 jugs high, we’d have a nice little cube that would sit almost perfectly on the square that surrounds the U.S. Capitol.

If President Biden were to leave the White House and head to a building across the street to regard the petroleum reserve in its Capitol-submerging milk-jug format, it would look like this.

Of course, this storage process does introduce a few foreseeable problems. The Capitol would be unusable, for example, which has both positive and negative repercussions. It would be pretty common for some of those jugs to spring a leak, and quite a problem if one in the middle of the cube were to do so. Not to mention that it is not particularly smart to build a strategic reserve of something in a way that a ne’er-do-well could sabotage dramatically with a BB gun. So, as it turns out, this is not how the government stores all of that oil.

What it does instead is store it in four locations around the Gulf Coast. Were it held in oil silos, those cylindrical structures you see around refineries, it would require nearly 64,000 such silos to contain the country’s current reserve — a massive amount requiring a massive amount of infrastructure. (If the reserve were filled to its allowed limit of 714 million barrels, we’d need nearly 80,000 silos.) Those structures, too, would be at risk of damage.

Instead, we store that oil underground. It’s pretty ingenious, really; when the reserve was created, the government used water to carve massive caverns out of underground salt deposits, forcing water in and extracting a saltwater brine to create space for the oil. The largest storage facility, Bryan Mound in Freeport, Tex., has 19 caverns in which more than 247 million barrels can be stored.

A 1977 proposal to build the site explains how the oil would be inserted and removed. A nested set of tubes pushes oil in and allows brine to escape. (Oil, as you’ll recall from making pasta and/or school, floats on water.) Then, when oil is needed, water is injected and the oil forced up and out.

We can do some back-of-the-envelope math to figure out that the caverns at Bryan Mound are about 64,400 cubic yards big on average. That’s about a fifth of the size of the Hindenburg.

Biden has authorized the release of up to a million barrels of oil a day through the country’s network of pipelines. Were he instead to have it put in 42 million milk jugs, it would be enough to fit in somewhere north of 5,000 semi tractor-trailers.

Bringing a convoy like that to the capital every day, it’s safe to say, would shut things down.